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In computer science and mathematical logic, an infinite tree automaton is a state machine that deals with infinite tree structure. It can be viewed as an extension from a finite tree automaton, which accepts only finite tree structures. It can also be viewed as an extension of some infinite word automatons such as the Büchi automaton and the Muller automaton. A finite automaton which runs on an infinite tree was first used by Rabin〔Rabin, M. O.: ''Decidability of second order theories and automata on infinite trees'',''Transactions of the American Mathematical Society'', vol. 141, pp. 1–35, 1969.〕 for proving decidability of monadic second order logic. It has been further observed that tree automaton and logical theories are closely connected and it allows decision problems in logic to be reduced into decision problems for automaton. ==Definition== Infinite tree automaton runs of over a -labeled tree. There are many slightly different formulations of tree automaton. Here one of the formulation is described. An infinite tree automaton is a tuple where, * is an alphabet. * is a finite set. Each element of is an allowed degree in input tree. * is a finite set of states. * is a transition relation that maps an automaton state , an input letter , and a degree to a set of d-tuple of states. * is an initial state of automaton. * is an accepting condition. 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Infinite tree automaton」の詳細全文を読む スポンサード リンク
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